Restoration and interpretation of images from the Yohkoh Soft X-Ray Telescope Original Research Article

Due to the finite width of the point spread function (PSF) of the Yohkoh Soft X-Ray Telescope (SXT) mirror, a certain amount of blurring effect is inevitable in the observed soft X-ray images. Thus it is necessary to subtract its effect from the observed images for both morphological and photometric purposes. Because of undersampling due to a large pixel size of the CCD camera of SXT, however, the application of general algorithms to image restoration has so far been unsatisfactory for the SXT images. Therefore, we have developed a new method for increasing the sampling density of Yohkoh SXT images under the condition of photon number conservation in each pixel. The correction for the undersampling effect was also necessary to obtain a good estimate of the PSF from the ground experimental data. Based on this best-fit PSF, we apply the maximum entropy method algorithm to the observed SXT images. The restored images succeed in showing fine details in coronal loops, but there still remains the problem of insufficient noise suppression.